Agricultural chemicals used as fertilizers, pesticides, herbicides, and the like, are prone to erosion and leaching from treated soils and plants. For example, fertilizers that are applied to fields can suffer run-off or loss caused by rapid watering, rain, or other water exposures. As another example, chemicals that are applied to foliar surfaces are prone to loss due to erosion from treated plants. As yet another example, pre-emergent agents (i.e., those agents that are applied to the soil before the germination of plants or weeds) need to stay where they are applied for a period of time while the plants and/or weeds are germinating. Dissipation of a pre-emergent agent by microbial activity, photodegradation, chemical degradation, run-off by water exposure, and the like, is undesirable during the germination period, and it is advantageous that the agent be retained in the top one or two inches of soil during this period. These problems are especially important for optimizing the properties of agents that need to act over a prolonged period of time to obtain their desired effect, as opposed to those agents that exert their effects immediately, like, for example, a pesticide that kills on contact. Without improved retention properties, agricultural chemicals can be washed off with rain or can be wiped off too easily.
As an example, protection of pre-harvest fruits/nuts/vegetables is of paramount importance. Growing fruits or vegetables on the trees and vines and bushes are prone to pest infestation and their tender skins are prone to sunburns reducing the overall yield of these products. In new farming methods, there is a push to reduce or eliminate the amount of synthetic pesticides that are used, particularly on fruits or vegetables with edible skins. To help overcome pest problems, these fruits or vegetables are often sprayed with particles capable of forming a barrier layer to prevent pest infestation and to prevent sunburns. In some other fruits such as cherries and tomatoes, even accumulation of water at the stems of the fruit leads to imbibition of water leading to osmotic imbalance inside the fruit resulting in unsightly cracking of fruit skin. To prevent this, there is a need for a breathable, benign and rainfast barrier coatings. There remains a need in the art for nontoxic alternatives to the use of pesticides to protect agricultural materials from insects, fungi, animals, drought conditions, air pollution damage, and solar damage. Furthermore, a need exists to improve herbicide performance by (1) enhanced retention of the active ingredients in the topsoil, (2) prevention of active ingredient leaching (i.e., sustained release) and (3) protection of the herbicides against photodegradation. There is a particular need for pre-harvest fruit/nut/vegetable protection because of the high value of these crops and the demand for organic produce.
A new generation of herbicides and other such agricultural treatment agents are biologically derived. For example, there are biological control agents that require delivery to agricultural targets, where retention and/or controlled release of those agents in proximity to the agricultural target is desired. As used herein, the term “agricultural target” is selected from the group consisting of a leaf, a fruit, a vegetable, a seed or seed case, a stem, a post-harvest agricultural product, and a soil, agricultural growth medium, or other agricultural substrates as would be understood by those of ordinary skill in the art. Desirably, a delivery formulation providing improved retention properties would be suitable for use with biological control agents.
Herbicides, insecticides, fungicides, plant growth regulators, insect pheromones, nutrients and other agricultural treatment agents are also advantageously used in spraying fruits or vegetables and plants directly. For example, cocoa pods can be afflicted by “black pod” disease, treated by spraying the pods with both fungicides and insecticides. Black pod is a plant disease caused by Phytophthora type oomycetes such as Phytophthora infestans, the pathogen that caused the Irish potato famine. Enhanced retention of the treatment agents on the target (e.g., the cocoa pod) can improve their efficacy and improve the efficiency of treatment protocols. A naturally derived coating for the cocoa pods could also create a physical barrier (i.e., a barrier coating composition, formed for example as a film) to deter pests, and could reduce or eliminate the need for additional treatment agents.
Agricultural treatment agents (pesticides, fertilizers, plant growth regulators, and the like) are costly and can cause environmental damage if misused. There is a need for materials and methods to improve the efficiency and costs associated with the use of agricultural treatment agents, or to reduce or eliminate the need for agricultural treatment agents.